It has been typical in the processing of powdered metal parts which have been prepared from materials such as atomized powdered metals which are then sintered, to also subject the hardened parts to plating. The plating, such as a zinc electroplating, can add to the corrosion resistance of the finished part. Resin impregnation may also be useful.
Some resin impregnation might even precede plating. Thus it has been disclosed in U.S. Pat. No. 3,007,822 to resin impregnate a hardened powdered metal part and then carbonize the resin followed subsequently by a carbo-nitriding process. In this manner enhanced substrate for plating can be prepared.
Resin impregnation can also be used in conjunction with oil-impregnation. Thus for example U.S. Pat. No. 4,014,802 discusses sintered parts having both an oil-impregnated portion as well as a resin-impregnated layer. The useful resin can be a thermosetting resin. Or the resin material might be useful for lubricating property.
It has been disclosed in U.S. Pat. No. 4,000,982 that it is well known for a porous sintered layer of iron or copper powder, which might be used in a bearing to be coated with a polytetrafluoroethylene resin. Within the specific teachings of the patent, there is taught the improvement of using such a resin as a dispersion, with the dispersion containing powdered zinc and aluminum oxide. An article of excellent wear-resistance is thereby prepared.
It would still nevertheless be desirable to treat porous, sintered metals in an economical manner and yet efficiently achieve a part of outstanding corrosion resistance.